In diabetes mellitus, the body either fails to produce or to respond to insulin, which regulates glucose metabolism, resulting in large fluctuations in glucose levels. These fluctuations can cause a range of secondary complications, including kidney disease, heart disease, blindness, nerve damage, and gangrene. Current treatment of diabetes consists of self-regulation of blood glucose levels through frequent monitoring and a combination of diet, medication, and insulin injection, depending on the type of diabetes. Most patients measure their glucose levels by withdrawing small samples of blood using a “finger-stick” apparatus followed by electrochemical detection of an oxidation product of glucose. This type of measurement is both painful and inconvenient. As a result, many patients fail to adequately monitor their glucose levels, risking secondary complications. A faster, easier, and less painful method for frequently measuring glucose levels would be of great individual, clinical, and societal benefit. Continuous monitoring of blood glucose would open the door to feedback control of implanted insulin pumps. A reliable and robust sensor technology is the single stumbling block in an artificial pancreas.